1. Field of the Invention
The present invention relates to a magnetic tape cassette suitable for use as a video tape cassette, and more particularly to a magnetic tape cassette having a reel-locking member with reduced susceptibility to engagement fatigue. Engagement fatigue is a frequent cause of failure and/or breakage of the reel-locking members of the conventional magnetic tape cassettes.
2. Description of the Related Art
FIG. 1 illustrates an inside structure of a conventional magnetic tape cassette. A video tape cassette 5 provides a cassette half 51 (an upper cassette half is removed for clarity, and hence only a lower cassette half is illustrated in FIG. 1) in which a pair of reels 52 and 53 are disposed for rotation. Around each of the reels 52 and 53 is wound a magnetic tape 54. The magnetic tape 54 is guided by tape guides 55 and 56 disposed in the vicinity of a front (an upper side in FIG. 1) and at opposite sides of the cassette 5 so that the magnetic tape 54 passes above an opening 57 formed in the vicinity of the front of the cassette half 51. Lower flanges 58, 59 of the reels 52, 53 are formed at a whole peripheral thereof with teeth 60, 61.
For instance, Unexamined Japanese Patent Publication No. 7-14342 has suggested a lock member 62 which is disposed in an almost triangular space 70 located in the vicinity of a rear of the cassette case and between the pair of the reels 52, 53 and which acts as a reel locking device for preventing the reels 52, 53 from rotating in order not to loosen the wound magnetic tape 54 in transportation and handling thereof while the video tape cassette is not loaded in a video deck (not shown).
The conventional lock member 62 is formed with almost triangular shaped ribs 80 and 81 between a rear plate 63 of the cassette half 51 and the pair of reels 52 and 53. The ribs 80 and 81 have straight portions extending in a front-rear direction of the cassette half and parallel to each other, and an engagement member 67 is slidably interposed between the straight portions 65 and 66. A compressed spring 68 disposed between the rear plate 63 and the engagement member 67 supplies the engagement member 67 with a pushing force towards the front of the cassette half. The engagement member 67 is formed at a bottom surface thereof with an opening 69 through which a lock-releasing pin of a video deck is to be inserted. The cassette half 51 is formed at a bottom surface thereof with an opening (not shown) located correspondingly to the opening 69 of the engagement member 67.
The engagement member 67 is suitably made of elastic resin, and has a rectangular-shaped slide body 71 having a relatively wide bottom surface area for stable slide movement, as illustrated in FIG. 2. The slide body 71 is integrally formed at a front face thereof with a pair of engagement claws 72 and 73 which are engagable to the teeth 60, 61 of the reels 52, 53.
The engagement claws 72 and 73 are designed to be relatively long and to have thin hinge portions 74, 75, respectively, at the proximal ends of the engagement claws 72 and 73, that is, at joint portions connecting the engagement claws 72, 73 to the slide body 71. Thus, the engagement claws 72 and 73 are able to elastically and transversely swing as shown with arrows A in FIG. 2. As illustrated in FIG. 2, a guide device such as pins 90 is disposed on the cassette half 51 in a projecting fashion. The pins 90 ensure that the engagement claws 72 and 73 open relative to each other to thereby engage to the teeth 60, 61 for locking the reels 52 and 53 as the slide body 71 slides towards the front of the cassette half, and that the engagement claws 72 and 73 close relative to each other or move towards each other to thereby move away from the teeth 60, 61 for releasing the reels as the slide body 71 slides towards the rear of the cassette half.
In the conventional video tape cassette 5, the engagement claws 72 and 73 are designed to be elongated and to have the hinge portions 74 and 75 by forming the proximal ends of the engagement claws 72 and 73 to be thin so that the engagement claws 72 and 73 of the engagement member 67 of the lock member 62 are transversely swingable. Thus, the hinges 74 and 75 are often fatigued when the video tape cassette 5 falls on a floor or by long term use, for instance, so that the engagement claws 72 and 73 are broken at the hinge portions 74 and 75 or are deformed with the result of uncertain lock of the reels 52 and 53. In addition, when the engagement member 67 is handled as a unitary part prior to cassette assembling, the engagement claws 72 and 73 may be undesirably damaged. Thus, much attention is to be paid to the engagement claws 72 and 73.
On the other hand, there has been suggested a magnetic tape cassette in which the engagement claws are prepared separately from the slide body, and the engagement claws are secured to the cassette half for rotation. The slide movement of the slide body causes the engagement claws to rotate to thereby engage distal ends of the engagement claws to the teeth of the reels. For instance, refer to Unexamined Japanese Patent Publication No. 6-44733. However, this magnetic tape cassette has to have a greater number of parts since the engagement claws are formed separately from the slide body, and has much complexity in assembling thereof. In particular, each of parts has to be small in a small-sized magnetic tape cassette. Thus, if there are a great number of parts, assembling of the cassette takes too much time and labor. For this reason, the lock member which is to be assembled is not preferable. The above mentioned problem also arises in various types of magnetic tape cassettes as well as the video tape cassette 5.